Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
  • C09K8/524—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning organic depositions, e.g. paraffins or asphaltenes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F22/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides or nitriles thereof
  • C08F22/36—Amides or imides
  • C08F22/38—Amides
  • C08F22/385—Monomers containing two or more (meth)acrylamide groups, e.g. N,N'-methylenebisacrylamide
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/04—Acids; Metal salts or ammonium salts thereof
  • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
  • C09K8/528—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning inorganic depositions, e.g. sulfates or carbonates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
  • C09K2208/10—Nanoparticle-containing well treatment fluids
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
  • C09K2208/26—Gel breakers other than bacteria or enzymes

Definitions

• the present invention relates to compositions for providing gradual release of agents of the type that inhibit the formation of inorganic or organic deposits (in particular scale inhibitors) in underground formations such as hydrocarbon reservoirs.
• hydrocarbon reservoir oil reservoir such as a consolidated or unconsolidated rock formation, or a sand, for example
• various factors can induce the formation of deposits, the formation of which it is important to inhibit in order to prevent phenomena of obstruction of the underground formation (rock and/or well), which otherwise result in a slowing or even stopping of production.
• Various types of deposits can form in a hydrocarbon reservoir, such as scale (essentially inorganic deposits based on calcium carbonate, barium sulfate, strontium sulfate, calcium sulfate and/or calcium fluoride, in particular) or else asphaltene or wax deposits, or alternatively methane hydrate deposits.
• a method commonly used to try to limit the formation of deposits of this type consists in injecting under pressure, into the underground formation, an aqueous composition comprising inhibitors, typically according to a step termed a “squeeze” step.
• aqueous composition comprising inhibitors
• One difficulty during the implementation of steps of this type is that, in general, only a small amount of injected inhibitors is effective in providing the desired inhibition effect, in particular because a large part of the agents injected is immediately removed in the stream of production fluids during restart of the well following the “squeeze” step. This removal of a large part of the agents introduced has in particular a negative impact in terms of costs.
• it creates limited inhibitor contents in the underground formation, which can prove to be too low to provide the desired inhibition effect, which often requires maintaining a minimum inhibitor concentration in the formation.
• a more specific method that has been proposed, and that is described in particular in WO 03/106810, consists in using inhibitors in the form of microgels, obtained by reacting inhibitors of carboxylic acid type with polyols providing crosslinking by formation of multiple ester bonds.
• the size of the microgels formed is not controlled, and it results in the formation of objects of relatively large sizes (of about a few microns), which, once again, are likely to damage the underground formation, sometimes irreversibly.
• An objective of the present invention is to provide a novel method for obtaining the advantages of the abovementioned methods, but while avoiding the drawbacks thereof.
• an objective of the present invention is to provide the means for inhibiting the rapid loss of inhibitors after injection thereof into an underground formation, but without, in order to do this, having to run the risk of damaging the underground formation, and in particular the risk of blocking the pores of the rock.
• the present invention proposes using polymeric inhibitors in the form of polymer chains which are crosslinked with one another by means of crosslinking agents which tend to gradually degrade under the temperature and/or pH conditions of the underground formation where they are introduced, these crosslinked chains having specifically the form of objects of very small size (nanogels), thereby limiting the blocking phenomena encountered with the abovementioned methods proposed in the prior art.
• a subject of the present invention is a composition
• a solvent medium S typically in an aqueous solvent, for example water or a water/alcohol mixture, which is optionally additivated
• chemically crosslinked polymers P resulting from the radical copolymerization of a mixture of monomers including:
• the term “cleavable group” is intended to mean an at least divalent group, present in a chain, which is stable at least under certain pH and temperature conditions, but which is lysed, inducing a chain cleavage, when it is subjected to a temperature above a limiting temperature (thermal cleavage) and/or when it is placed under specific pH conditions (pH-induced cleavage).
• the lysis of the cleavable group(s) present on the chain is preferably carried out irreversibly and without lysing the rest of the chain.
• the polymers P present in the compositions of the invention comprise such cleavable groups, which are introduced into the chains and ensure crosslinking thereof via the use of the monomers m2.
• the cleavable groups present on the polymers P are generally identical to those present on the monomers m2 and they are typically -ester-; -amide-; -ether-; -ether phosphate-; alternatively -ether sulfate-divalent groups. According to one advantageous embodiment, they are ester or amide groups, in particular an ester function.
• the polymers P are synthesized under pH and temperature conditions where said cleavable groups are stable.
• the monomers m1 preferably do not bear cleavable groups.
• the cleavable groups all constitute “fragilities” which induce a gradual loss of the crosslinking when the polymers are subjected to cleavage-inducing temperature and/or pH conditions.
• the temperature conditions required are typically obtained when a composition of the invention is injected into an underground formation and the pH conditions may be obtained at any time, as required, by injection of a base or of an acid so as to obtain the cleavage pH.
• compositions according to the invention thus comprise polymers in a crosslinked form, thereby giving them better retention in the underground formation than polymers in noncrosslinked form.
• This crosslinking makes it possible, as a result, to retain a considerable part of the polymers in the formation by inhibiting the premature departure thereof before they can provide the desired effect of inorganic or organic deposit formation inhibition.
• this crosslinking of the polymers P is, however, temporary and, through gradual cleavage, the polymers P introduced into an underground formation are thus capable of continuously releasing over time polymer chains suitable for providing an effect of inorganic or organic deposit formation inhibition, as required, by adjusting the pH in the underground formation, for example by coinjection of a base or of an acid.
• the crosslinking-monomer-based chains gradually disappear, to be replaced by noncrosslinked or very sparingly crosslinked polymers.
• the method of the invention makes it possible, depending on the temperature and pH conditions prevailing in the underground formation where the use of the composition is envisioned, to adapt the polymer used, so as to obtain the desired release profile.
• the release rate can be adapted by adjusting the nature of the cleavable group (the more fragile the group is, the more rapidly it will be released) and the number of crosslinking monomers in the polymer (the more of these crosslinking monomers there are, the lower the release rate).
• the polymers according to the invention are in the form of objects of very small size, less than 100 nm, which will be denoted in the present description by the generic term “nanogels”.
• nanogels This specific use of nanogels, much smaller in size than the crosslinked objects proposed in the prior art methods (much smaller in size than the microgels of WO 03/106810, in particular) have the advantage of inducing many fewer underground formation degradation phenomena (the risks of blocking the oil-producing rock are in particular greatly reduced).
• the size to which reference is made here is the average hydrodynamic diameter of the polymers in the composition as measured by dynamic light scattering or else the average radius of gyration of the polymers in the composition, measured by static light scattering.
• the polymers P are present in the form of objects having a radius of gyration of less than 100 nm, preferably less than 75 nm, for example between 1 and 50 nm. These very small sizes are easily attainable by radical polymerization of the monomers m1 and m2. This size may be even further controlled by using a controlled radical polymerization carried out in the presence of a control agent.
• the polymers P are obtained via a radical polymerization of the monomers m1 and m2 which is specifically carried out in solution (the monomers are dissolved in a solvent in which the polymers formed are soluble).
• the radical solution polymerization is advantageously carried out using the solvent medium S of the composition of the invention (typically water or a water/alcohol mixture, which is optionally additivated) as polymerization solvent, thereby making it possible to directly obtain the composition resulting from the polymerization.
• the solvent medium S of the composition of the invention typically water or a water/alcohol mixture, which is optionally additivated
• the solvent medium S is aqueous and monomers m1 and m2 which result in the formation of water-soluble polymers are used.
• monomers such as NIPAM, which are water-soluble, but which form polymers that precipitate in water during their formation.
• the monomers m1 and m2 are different than NIPAM and, more generally, the monomers m1 and m2 are preferably monomers which are not capable of forming polymers which are water-insoluble, at least under certain temperature conditions.
• the monomers m1 and m2 are preferably not monomers capable of forming polymers having an LCST (lower critical solution temperature).
• the polymers P result from a controlled radical polymerization of the monomers m1 and m2, carried out in the presence of a control agent.
• the nanogels obtained are, schematically, based on polymer chains of poly (m1) type, namely polymers (homo- or copolymers) based on the structuring monomers m1, crosslinked with one another as in the most general case (taking into account the use of the monomers m2), but which also have the specificity, according to this particular mode, of all having approximately identical lengths (taking into account the presence of the control agent).
• the implementation of a controlled radical polymerization makes it possible to very finely adjust the delivery profile and the anti-scale-type inhibition effect desired according to the invention.
• the polymers P result from a controlled radical polymerization of the monomers m1 and m2, carried out in the presence of a control agent and also performed in solution, preferably under the abovementioned conditions.
• a subject of the present invention is a preparation process which is particularly suitable for synthesizing compositions of the abovementioned type with the small size desired for microgels.
• This process comprises a step (E), preferably carried out in solution, in which the following are brought together:
• the amount of control agent relative to the total amount of monomers (control agent)/(m1+m2) is between 0.1% and 10%, preferably between 0.15% and 5%.
• step (E) When step (E) is carried out in solution, it is carried out in a solvent medium (advantageously the solvent medium S of the composition of the invention) in which the monomers m1 and m2, the source of free radicals and the control agent are all soluble, typically in an amount of at least 1 g/l in the solvent under the conditions of step (E).
• a solvent medium advantageousously the solvent medium S of the composition of the invention
• the source of free radicals and the control agent are all soluble, typically in an amount of at least 1 g/l in the solvent under the conditions of step (E).
• a subject of the invention is the use of the abovementioned composition as an inhibitor of the formation of inorganic or organic deposits, such as scale, in an underground formation in the context of an oil extraction.
• the composition according to the invention is injected into an underground formation, typically during a “squeeze” step of the abovementioned type.
• Any monomer of which the resulting polymer is known to induce an effect of inhibition of the formation of inorganic and/or organic deposits such as scale can be used as structuring monomer m1 according to the invention.
• the monomers m1 can typically be acrylic acid monomers, which result in the formation of poly(acrylic acid), well known as an inhibitor of the formation of barium sulfate scale.
• monomers m1 according to the invention of (in particular anhydrides, esters and chlorinated derivatives such as acid chlorides), these acids and derivatives which are of use as monomers m1 according to the invention typically being selected from:
• Compounds which are advantageous as monomers m1 are acrylic acid, methacrylic acid, ethacrylic acid, ⁇ -chloroacrylic acid, bromoacrylic acid, bromomethylacrylic acid, ⁇ -cyanoacrylic acid, ⁇ -methylacrylic acid, ⁇ -phenylacrylic acid, ⁇ -acryloxypropionic acid, ⁇ -carboxyethylacrylic acid (oligomerized acrylic acid, and in particular of the abovementioned Sipomer B-CEA type), cinnamic acid, itaconic acid, maleic acid, glutaconic acid, aconitic acid, fumaric acid, vinylbenzoic acid, propylacrylic acid, maleimidopropylcarboxylic acid; and mixtures of these compounds.
• the monomers m1 When the monomers m1 contain acid groups, they may be used during their polymerization in free acid form (—COOH for example) or else in a totally or partially neutralized form (carboxylate groups or mixture of carboxylates and —COOH, for example).
• Monomers m1 which are very suitable according to the invention, used in the examples given hereinafter, are acrylic acid, sodium vinyl sulfonate, styrenesulfonic acids and/or vinylphosphonic acid.
• They are typically monomers bearing two ethylenically unsaturated groups, separated by a spacer group including at least one cleavable group of the abovementioned type.
• They may in particular be monomers of formula H 2 C ⁇ C-A-C ⁇ CH 2 , where A denotes a saturated or unsaturated, linear or branched and optionally totally or partially cyclized, divalent hydrocarbon-based chain, for example an alkylene or alkenylene chain, said chain including a cleavable group.
• Suitable crosslinking monomers include in particular acrylic esters, methacrylic esters, diallyl ethers and divinyl ethers of alcohols bearing at least two hydroxyl groups (hereinafter denoted “dihydric” alcohols, this term not being intended to denote herein only alcohols bearing exactly two —OH groups, but more broadly any alcohol bearing at least two OH groups, it being possible for the OH groups of these alcohols to be totally or partially etherified or esterified).
• Suitable monomers m2 thus include, for example, acrylic esters, methacrylic esters, diallyl ethers and divinyl ethers of the following dihydric alcohols:
• polyethylene glycols and/or polypropylene glycols is intended to mean herein the group consisting of ethylene oxide homopolymers (polyethylene glycols), propylene oxide homopolymers (polypropylene glycols), and copolymers based on ethylene oxide and on propylene oxide, in particular block copolymers comprising at least one polyethylene oxide block and at least one polypropylene oxide block.
• Dihydric alcohols which are very suitable in the abovementioned esters and ethers are trimethylolpropane, glycerol, pentaerythritol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, sorbitan, or else sugars, such as, inter alia, sucrose, glucose or mannose.
• dihydric alcohols may advantageously be used in the form of ethoxylates or propoxylates, namely respectively after reaction with ethylene oxide or propylene oxide.
• glycidyl ethers which are obtained by reacting polyhydric alcohols with epichlorohydrin.
• Monomers m2 which are very suitable according to the invention, used in the examples given hereinafter, are diethylene glycol diacrylate (termed “DiEGDA”) and N,N′-methylenebisacrylamide (termed “MBA”).
• acrylamido or methacrylamido compounds in particular N,N′-methylenebisacrylamide, N,N′-methylenebismethacrylamide, glyoxal bisacrylamide, or diacrylamidoacetic acid.
• Step (E) of the process of the present invention which makes it possible to synthesize the polymers P by controlled radical polymerization, is specifically carried out in the presence of a control agent.
• any agent known per se as suitable for controlling the radical polymerization of the monomers (m1) and (m2) can be used in step (E).
• control agent used in step (E) is a compound bearing a thiocarbonylthio group —S(C ⁇ S)—.
• control agent may bear several thiocarbonylthio groups. It may optionally be a polymer chain bearing such a group.
• control agent may, for example, correspond to formula (I) below:
• the groups R 1 or Z when they are substituted, may be substituted with optionally substituted phenyl groups, optionally substituted aromatic groups, saturated or unsaturated carbocycles, saturated or unsaturated heterocycles, or groups selected from the following: alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxyl (—COOH), acyloxy (—O 2 CR), carbamoyl (—CONR 2 ), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (—OH), amino (—NR 2 ), halogen, perfluoroalkyl C n F 2n+1 , allyl, epoxy, alkoxy (—OR), S-alkyl, S-aryl, groups of hydrophilic or ionic nature such as alkali metal salts of carb
• the optionally substituted alkyl, acyl, aryl, aralkyl or alkyne groups generally contain 1 to 20 carbon atoms, preferably 1 to 12 and more preferentially 1 to 9 carbon atoms. They may be linear or branched. They may also be substituted with oxygen atoms, in particular in the form of esters or sulfur or nitrogen atoms.
• alkyl radicals mention may be made in particular of the methyl, ethyl, propyl, butyl, pentyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, decyl or dodecyl radical.
• the alkyne groups are radicals generally containing from 2 to 10 carbon atoms, and contain at least one acetylenic unsaturation, such as the acetylenyl radical.
• the acyl group is a radical generally containing from 1 to 20 carbon atoms with a carbonyl group.
• aryl radicals mention may be made in particular of the phenyl radical, optionally substituted in particular with a nitro or hydroxyl function.
• aralkyl radicals mention may be made in particular of the benzyl or phenethyl radical, optionally substituted in particular with a nitro or hydroxyl function.
• R 1 or Z is a polymer chain
• this polymer chain may be derived from a radical or ionic polymerization or derived from a polycondensation.
• compounds bearing a xanthate —S(C ⁇ S)O—, trithiocarbonate, dithiocarbamate or dithiocarbazate function for example bearing an O-ethyl xanthate function of formula —S(C ⁇ S)OCH 2 CH 3 , are used as control agent for step (E).
• Xanthates prove to be most particularly advantageous, in particular those bearing an O-ethyl xanthate function —S(C ⁇ S)OCH 2 CH 3 , such as O-ethyl-S-(1-methoxycarbonylethyl)xanthate (CH 3 CH(CO 2 CH 3 ))S(C ⁇ S)OEt manufactured by Rhodia under the name Rhodixan® A1.
• control agent in the polymerization reaction makes it possible to finely control the size of the polymer chains and to synthesize polymer chains which are all of approximately identical size and morphology, thereby making it possible to very finely and very precisely modify the properties of the nanogel.
• step (E) of the process of the invention Any source of free radicals which is known per se as being suitable for processes for polymerizing the selected monomers m1 and m2 may be used in step (E) of the process of the invention.
• the radical polymerization initiator may, for example, be selected from the following initiators:
• a radical initiator of redox type which has the advantage of not requiring heating of the reaction medium (no thermal initiation).
• the source of free radicals that is used can typically be selected from the redox initiators conventionally used in radical polymerization, typically not requiring heating for thermal initiation thereof. It is typically a mixture of at least one water-soluble oxidizing agent with at least one water-soluble reducing agent.
• the oxidizing agent present in the redox system may be selected, for example, from peroxides such as: hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctoate, t-butyl peroxyneodecanoate, t-butyl peroxyisobutyrate, lauroyl peroxide, t-amyl peroxypivalate, t-butyl peroxypivalate, dicumyl peroxide, benzoyl peroxide, sodium persulfate, potassium persulfate, ammonium persulfate or potassium bromate.
• peroxides such as: hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-but
• the reducing agent present in the redox system may typically be selected from sodium formaldehyde sulfoxylate (in particular in dihydrate form, known under the name Rongalit, or in the form of an anhydride), ascorbic acid, erythorbic acid, sulfites, bisulfites or metasulfites (in particular alkali metal sulfites, bisulfites or metasulfites), nitrilotrispropionamides, and tertiary amines and ethanolamines (which are preferably water-soluble).
• sodium formaldehyde sulfoxylate in particular in dihydrate form, known under the name Rongalit, or in the form of an anhydride
• ascorbic acid in particular in dihydrate form, known under the name Rongalit, or in the form of an anhydride
• sulfites bisulfites or metasulfites
• nitrilotrispropionamides in particular alkali metal sulfites, bisul
• Possible redox systems comprise combinations such as:
• An advantageous redox system comprises (and preferably consists of) for example a combination of ammonium persulfate and sodium formaldehyde sulfoxylate.
• Examples 1 to 9 below describe the protocol used to synthesize various polymers (control polymers and polymers in the form of “nanogels” according to the invention). After each polymerization, the final solution was analyzed by the “Gel Permation Chromatography-Multi Angle Laser Light Scattering” (GPC-MALLS) method which makes it possible to measure the weight-average molecular weight (Mw) of the species present.
• GPC-MALLS Global Permation Chromatography-Multi Angle Laser Light Scattering
• the conditions used for the GPC-MALLS are the following:
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the molar mass measured by 1 H NMR is 8761 g/mol.
• the solids content (115° C., 1 h) is 34.6 w/w %.
• the degree of conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 5200 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the molar mass measured by 1 H NMR is 11 691 g/mol.
• the solids content (115° C., 1 h) is 35.1 w/w %.
• the degree of conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 9100 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 26.5 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 144 400 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 29.3 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 65 220 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 30.0 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 116 700 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 30.0 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 116 700 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 29.0 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 31 280 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it and then adjusting the pH thereof to 3.4 with sodium hydroxide at 50 wt %.
• This medium is then concentrated under reduced pressure using a rotary evaporator, until a solid concentration of 49.8 wt % is obtained (115° C., 60 min).
• This solution is reintroduced into the three-necked reactor, and 9.9 g of NaSS are added thereto.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 25.9 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 105 000 g/mol.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it and then adjusting the pH thereof to 2.6 with sodium hydroxide at 50 wt %.
• This medium is then concentrated under reduced pressure using a rotary evaporator, until a solid concentration of 44.7 wt % is obtained (115° C., 60 min).
• This solution is reintroduced into the three-necked reactor, and 4.9 g of VPA are added thereto.
• the reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.
• the reaction medium is brought to 70° C. with stirring.
• the solids content (115° C., 1 h) is 20.0 w/w %.
• the degree of acrylic acid conversion measured by HPLC is 100%.
• the average molar mass measured by GPC-MALLS is 72 270 g/mol.
• the polymers prepared were evaluated under static conditions, according to the methodology known as the “Jar test” or “Bottle test”, which consists in measuring the level of precipitating cation (calcium or barium) soluble after mixing of two incompatible waters in a flask, then evolution of the mixture without stirring for a given time, and measurement of the soluble cations by a spectroscopic method (ICP-AES).
• the experiments comprise a controlled test without inhibitor and tests in the presence of inhibitors.
• This evaluation is carried out at 95° C. and pH 5.5 after mixing of two brines, one of which has the composition of formation water from the FORTIES field in the North Sea (contains barium) and the other of which has the composition of seawater (contains sulfate).
• the inhibitor is placed in the seawater.
• the inhibitor concentration is 15 ppm (of active material) relative to the final mixture.
• the pH of the seawater solution containing the inhibitor is brought to approximately 5.5 with a sodium acetate/acetic acid buffer solution.
• compositions of the brines are the following:
• the content of the “FORTIES water” flask is poured into the flask containing the barium. Stirring is carried out manually, then the mixture is put back in the incubator at 95° C. for 2 h.
• the flasks are removed from the incubator and a 5 ml sample is taken, and then diluted in 5 ml of a “soaking” solution, the composition of which is: 5000 ppm of KCL/1000 ppm of PVS (sodium Poly(Vinyl Sulfonate)) adjusted to pH 8-8.5 (with 0.01 N NaOH).
• a barium assay is carried out on these samples (ICP-AES) and the inhibition efficiency, expressed according to the formula below, is deduced therefrom.
• This example illustrates the capacity of the nanogels according to the invention to release polymeric units when they are subjected to a temperature increase.
• the release will, for a given temperature, be more or less rapid.
• aqueous solutions are introduced into glass flasks, at their end-of-synthesis pH, and then degassed under nitrogen bubbling for 20 minutes. After the flasks have been closed, they are placed in an incubator for one week at constant temperature (75° C., 85° C. and 95° C.).
• GPC-MALLS Global Permation Chromatography-Multi Angle Laser Light Scattering
• the conditions used for the GPC-MALLS are the following:
• the table below specifies the pH of each heat-treated nanogel solution and recalls the “weight”-average molar mass measured by GPC-MALLS.
• Example 1 95° C. 144 85 32 21 18 11 12 5.2 85° C. 144 79 85 35 27 19 17 5.2 75° C. 144 69 55 43 / 35 / 5.2
• the inhibition efficiency of the nanogels was measured after a heat treatment, which once again demonstrates the release of the linear polymeric units, under the conditions hereinafter.
• the nanogels are evaluated according to the procedure described in example 10 and the BaSO 4 inhibition performance levels thereof are thus evaluated.
• the level of polymer in these “jar tests” is 15 ppm.
• the clay used as adsorption support is kaolinite. Its specific surface area measured according to the nitrogen BET method is 12 m 2 /g.
• the alumina used as adsorption support has a specific surface area of 200 m 2 /g measured according to the nitrogen BET method.
• a solution containing 1000 ppm of polymer or nanogel is prepared from this brine.
• the pH of these solutions is controlled: it is, after adsorption, 5.0 for the alumina support and 3.1 for the kaolinite support.
• the solid and also 30 g of solution containing a variable concentration of polymer or nanogel are then placed in glass flasks.
• the flasks containing the solid and the solution are closed and then stirred by hand and placed in an incubator at 85° C., in which they remain for approximately 15 hours.
• the supernatant is sampled hot, and the polymer concentration is measured on said supernatant by determining the amount of organic carbon by means of a TOC-meter (LabToc from Pollution & Process Monitoring). This level was also determined on the solutions before contacting.
• the level of polymer or of nanogel adsorbed at the surface of the solid is deduced therefrom, through the difference.
• the table below groups together the adsorptions measured, expressed in mg/g (mg of polymer or nanogel per g of solid); the C ini values represent the initial concentrations of polymer in the solution before adsorption, expressed in ppm.

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